/*
 * Zed Attack Proxy (ZAP) and its related class files.
 * 
 * ZAP is an HTTP/HTTPS proxy for assessing web application security.
 * 
 * Copyright 2013 The ZAP Development Team
 * 
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.zaproxy.zap.view.messagecontainer;

import java.util.List;

import org.zaproxy.zap.extension.httppanel.Message;

/**
 * A {@code MultipleMessagesContainer} that exposes the selected messages in the GUI component.
 * 
 * @param <T> the type of messages in this container
 * @see MessageContainer
 * @see MultipleMessagesContainer
 * @see SingleMessageContainer
 * @since 2.3.0
 */
public interface SelectableMessagesContainer<T extends Message> extends MultipleMessagesContainer<T> {

    /**
     * Tells whether or not there is at least one message selected.
     * 
     * @return {@code true} if at least one message is selected, {@code false} otherwise.
     */
    boolean hasSelectedMessages();

    /**
     * Tells whether or not only and only one message is selected.
     * 
     * @return {@code true} if only one message is selected, {@code false} otherwise.
     */
    boolean isOnlyOneMessageSelected();

    /**
     * Returns the selected message or {@code null} if none. If multiple messages are selected the first one is returned.
     * 
     * @return the selected message or {@code null} if none.
     */
    T getSelectedMessage();

    /**
     * Returns the number of selected messages.
     * 
     * @return the number of selected messages.
     */
    int getNumberOfSelectedMessages();

    /**
     * Returns all the selected messages or an empty {@code List} if none.
     * <p>
     * No assumptions should be made on the actual implementation type of the {@code List} returned by this method (for example,
     * it might be unmodifiable or its elements lazy loaded).
     * <p>
     * <strong>Note:</strong> Extra care should be taken when getting the messages from the list since it might return
     * {@code null} which indicate that an error occurred while getting a message (for example, failed to read a persisted
     * message).
     * 
     * @return a {@code List} with all the selected messages, never {@code null}.
     */
    List<T> getSelectedMessages();
}
